Exposure to high levels of indoor allergens(eg. from cockroaches and rodents) has been related to the high incidence of asthma morbidity and mortality in urban dwellers. We hypothesize that sustained reductions in residential exposures to indoor allergens can be achieved through interventions, allergen assessment and control and that the change in allergen exposures upon intervention will be associated with corresponding changes in both standard and novel measures of allergic sensitization among urban dwellers with asthma.